A conventional golf practice shelter is currently marketed under the trade mark WEATHERSTOPPER and includes a pair of end frames supported by ground engaging wheels and a canopy or roof frame to which a roofing sheet or canopy was attached. Each end frame included a horizontal wheel support rail which was also oriented transversely to the canopy frame to which an associated wheels were attached. Each end frame also incorporated a central upright which was attached to the wheel support rail. Each end frame also included an upper rail parallel to the horizontal wheel support rail and oblique bracing members interconnecting each end of the upper rail and a top end of the central upright. The canopy frame comprised a pair of lower longitudinal horizontal rails, a top horizontal longitudinal rail and a plurality of hoops located at spaced intervals along the length of the canopy frame. Each of the hoops were attached to a hoop support rail which was located outwardly of an adjacent lower horizontal longitudinal rail and parallel thereto. There was also provided angled bracing members, interconnecting each of the hoop support rails and the adjacent lower horizontal rail. There was also provided transverse bracing members interconnecting mutually opposite locations on each lower horizontal rail as well as diagonal horizontal bracing members interconnecting diagonally opposite locations on each lower horizontal rail. There was further provided oblique bracing members interconnecting each lower horizontal rail and the top horizontal rail.
The aforementioned WEATHERSTOPPER shelter structure was useful in that it enabled golf practice to occur in inclement weather. The shelter structure was also driven by heavy duty motors and there was 90 degree movement on all four wheels. It was also available in three different sizes i.e. having a length of 19 metres, 26 metres and 32.5 metres. Each wheel was attached directly to an associated wheel support rail by a horizontal axle so that each wheel was located laterally and outwardly of the wheel support rail.
It was found however in practice that while the WEATHERSTOPPER golf practice shelter was satisfactory in operation it was relatively complicated in structure in relation to the canopy frame because of the provision of a pair of longitudinal hoop support rails and the angled bracing members.
Another more significant disadvantage of the WEATHERSTOPPER golf practice shelter was that it was top heavy and thus had a tendency to be unstable in strong cross winds or cyclones. This meant that the canopy frame had a tendency to be subject to negative camber (i.e. wherein frame members may sag under strong cross winds) as well as positive camber (i.e. wherein frame members of the roof frame had a tendency to bow upwardly under strong cross winds).
Another disadvantage of the prior art was that each golf practice shelter was built at an installation site and thus was a “one-off” construction wherein the entirety of each of the frame members of the roof frame were fixedly or non adjustably attached to each other. This meant that construction was relatively expensive.
Reference may be made to U.S. Pat. No. 3,085,586, which describes a foldable tent structure having a pair of generally U-shaped end frames, which were relatively movably, interconnected by one or more tie elements which are maintained under tension as each of the end frames are moved from a collapsed to an erect position.
Reference also may be made to International Publication No WO 91/19872, which describes a method of erection of a tent having frame sections interconnected by longitudinal beams. Each frame section is located in spaced apart positions and hingedly attached to the longitudinal beams and elevated from an oblique position to a vertical position when erected.
U.S. Pat. No. 6,112,756 refers to a canopy support frame attached to a plurality of legs extending upwardly from the ground. The canopy support frame includes a plurality of support rods, which are each orientated in an oblique orientation on each side of the canopy frame, which each interconnect a top horizontal bar at the top of the canopy frame and a lower horizontal bar attached to a respective set of legs. Each of the support rods are interconnected on each side of the canopy frame by a tensionable wire to tension the overall frame structure when erected.
U.S. Pat. No. 4,173,857 refers to a double layered wooden arch truss for roof frameworks. There are provided stretchable chord members between each end of the arch truss to provide the arch members with greater strength. There also may be provided adjustable length turnbuckles constituting angle ties which interconnect a lower truss member and an adjacent upright.
International Publication No WO 95/27114 refers to a collapsible covered structure including a plurality of spaced arches and an awning dimensioned to be received within a space defined by opposed parts of each arch and wherein means are provided to suspend the awning to each arch.
DE 2356928 refers to a canopy frame having a pair of parallel U-sahaped horizontal rails and a plurality of flexible U-shaped hoops which have a plurality of spaced pulleys attached thereto interconnected by tensionable wires anchored to each U-shaped horizontal rail.
Reference is made to GB 1484236, which refers to a roof structure comprising a plurality of truss members interconnected by purlins. Each truss member has a top compression tube and a bottom tension tube connected together by vertical struts. The bottom tension tube has within it at least one high tension steel cable, which is tensioned during erection before being anchored at each end of the bottom tension tube.
The abovementioned prior art in the form of the WEATHERSTOPPER support structure had a particular disadvantage as a movable support structure, in that there was no means to effectively dissipate load bearing forces created by flexing of the frame members of the canopy frame during heavy winds. This led to instability in strong cross winds as stated above. The other prior art discussed above related mainly to frame structures which were not designed to be movable from place to place and, thus, could not be used as golf practice shelters.
It is therefore an object of the invention to provide a shelter structure which may alleviate at least one of the disadvantages discussed above.